Organopolysiloxane compositions containing an organopolysiloxane having aliphatic multiple bonds and an organohydrogensiloxane will cross-link in the presence of catalysts, which promote the addition of Si-bonded hydrogen to the aliphatic multiple bonds at room temperature to form elastomers. Generally, these compositions must be applied immediately after mixing, otherwise the mixture gels rapidly to a state where they can not be worked. Since these compositions gel very rapidly, they are not practical for some applications.
Accordingly, additives have been added to room temperature curable compositions containing organopolysiloxanes having aliphatic multiple bonds, organohydrogensiloxanes containing Si-bonded hydrogen and a platinum catalyst to inhibit curing of these compositions at room temperature. These compositions containing the additives are stable for extended periods of time at room temperature, but upon the application of heat at some future time, cure to an elastomeric solid.
Organopolysiloxane compositions containing various additives to inhibit curing at room temperature, are described for example in U.S. Pat. No. 3,192,181 to Moore which discloses an organosilicon compound containing (1) an organosilicon compound having on the average at least two monovalent radicals containing aliphatic unsaturation, (2) an organosilicon compound containing silicon-bonded hydrogen atoms, (3) a platinum catalyst and (4) benzotriazole, which prevents the platinum catalyst from catalyzing the reaction between SiH in (2) and the aliphatic unsaturated radicals in (1). Also, U.S. Pat. No. 3,445,420 to Kookootsedes et al disclose a mixture of an olefin containing organosilicon polymer, an organosilicon compound containing silicon-bonded hydrogen atoms, a platinum catalyst and an organic compound having a boiling point of at least 25.degree. C. and at least one --C.tbd.C-- group. The resultant composition does not cure as long as it is sealed from the air, but when exposed to air at room temperature or at low temperatures, is curable. Likewise, U.S. Pat. No. 3,882,083 to Berger et al discloses organopolysiloxanes which are stable at room temperature, but which are curable upon the application of heat comprising (1) an olefinorganopolysiloxane, (2) an organohydrogenpolysiloxane, (3) a platinum catalyst and (4) an ethylenically unsaturated isocyanurate which provides the compositions with latent curing properties. Organopolysiloxane compositions containing (1) an alkenyl polysiloxane, (2) a hydrogenpolysiloxane, (3) platinum catalyst and (4) nitrogen-containing compounds such as pyridine, dialkyl formamides and alkyl thioureas are described in U.S. Pat. No. 3,188,299 to Chalk. While these nitrogen-containing compounds reduce the activity of platinum catalysts in a temperature range of from 20.degree. to 30.degree. C., they do not inhibit curing at temperatures above about 40.degree. C.
In contrast to the organopolysiloxane compositions described above containing additives which retard or inhibit curing at room temperature, the organopolysiloxane compositions of this invention not only inhibit curing at room temperature, but also inhibit curing at temperatures in the range of from 40.degree. to 80.degree. C. However, at temperatures in excess of 100.degree. C. and especially at temperatures in excess of 150.degree. C., they cure very rapidly. Thus, the compositions of this invention may be easily worked at room temperature or at slightly elevated temperatures without premature gellation. This property is especially important in many industrial applications.
Therefore, it is an object of this invention to provide a thermosetting organopolysiloxane composition. Another object of this invention is to provide an organopolysiloxane composition which is essentially stable at temperatures up to about 80.degree. C. Still another object of this invention is to provide a composition which has an extended shelf-life even at temperatures slightly above room temperature. A further object of this invention is to provide a composition which is essentially stable at temperatures up to about 80.degree. C., but when heated to temperatures in excess of 100.degree. C., cures to a solid.